The Brain and the Heart are key elements to the framework of InsideOut.
The Brain represents the thoughts and the battles that are continually faced are all filtered through the brain. The battle of winning You Vs You starts in how you think.
The Heart is our second brain and is the core of our being. If you've ever felt heartache your subconscious mind may form an "energy wall" to protect your heart against further heartache. This wall of energy is the "Heart-Wall".